Elucidation of deformation and failure mechanisms of tensile-bolted connection in timber structures and development of evaluation methods

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K20458
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0304:Architecture, building engineering, and related fields
• Research Institution: Chiba University
• Principal Investigator: Totsuka Marina 千葉大学, 大学院工学研究院, 助教 (60893774)
• Project Period (FY): 2021-08-30 – 2024-03-31
• Keywords: 木質構造 / 引きボルト / 割裂 / 繊維方向圧縮

Outline of Final Research Achievements

This experimental and analytical study focused on tensile-bolted connections, which are one of the most commonly used joints in mid- to high-rise timber structures. It was found that tensile-bolted connections can fail by splitting, in addition to the well-known types of bolts yielding, compression yielding of the wood under the washer, shear failure of the wood, and bending failure of the wood. Split failure is a brittle failure, which means that the load drops to zero after the maximum bearing capacity. Furthermore, the cause of sprit failure was found to be the stress concentration around the bolts near the end grain.
A method using fracture mechanics was proposed to evaluate the spit failure, and it was confirmed that the experimental values could be generally evaluated. It was also shown that sprit fracture can be prevented by driving a self-tapping screw across the cross section of the wood.

Free Research Field

木質構造

Academic Significance and Societal Importance of the Research Achievements

本研究成果により，中高層木質構造に引きボルト式接合部を用いた場合の破壊モードを明確にできた。また，今まで破壊メカニズムがわかっていなかった引きボルト式接合部の割裂についてそのメカニズムを明らかにしたことで破壊荷重を予測できるようにした。また，引きボルト式接合部は柱脚だけでなく，柱梁接合部や梁の継手としてもつかわれる。提案する柱脚の評価法は鉛直荷重をゼロとすれば柱梁や梁継手に応用できる。